1. Field of the Invention
The invention relates to a thin film magnetic head having an inductive magnetic transducer for writing and a magnetic transducer for reading, and a method of manufacturing the same.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in an areal density of a hard disk drive. For example, a composite thin film magnetic head, which has a stacked structure comprising a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading, is widely used as the thin film magnetic head.
For example, the recording head includes a top pole and a bottom pole, which are located with a write gap in between on and under the write gap, respectively, and a coil for generating a magnetic flux with an insulating layer in between the top pole and the bottom pole. The top pole and the bottom pole have the same uniform width near the write gap in a region close to a recording-medium-facing surface (an air bearing surface) facing a magnetic recording medium (hereinafter referred to as “a recording medium”). The top pole and the bottom pole form “a magnetic pole portion” for determining a write track width. For example, the magnetic pole portion is formed in the following manner: the top pole having a uniform-width portion forming a part of the magnetic pole portion is formed, and then the write gap and the bottom pole are etched in self-alignment by using the uniform-width portion as a mask.
To increase the recording density of the performance of the recording head, it is necessary to locally miniaturize the width of the magnetic pole portion (a pole width) to the submicron order and thereby increase a track density on the recording medium. In this case, it is preferable that the pole width is uniform with high accuracy over the overall area of the magnetic pole portion. When the pole width is partly great, a side erase phenomenon occurs. Specifically, information is written not only on a track region on which the information is to be written, but also on a neighboring track region. Thus, information already written on the neighboring track region is overwritten with the information newly written thereon, and consequently the already-written information is erased.
Although the local miniaturization of the pole width to the submicron order is required, a problem has, however, heretofore existed: it is difficult to form with high accuracy the uniform-width portion of the top pole to be used as the mask for forming the magnetic pole portion. The problem arises for the following reason.
That is, for example, a coil for generating a magnetic flux is formed on a flat underlayer (e.g., a write gap), and then the coil is coated with an insulating layer made of a photoresist. As a result, a hill portion (hereinafter sometimes called “an apex portion”) made of the photoresist is formed on the flat underlayer. The apex portion has a round inclined surface near the edge thereof, for example because a portion near the edge flows due to heat treatment subjected to the photoresist with which a peripheral region around the coil is to be filled. To form the top pole made of a plated film pattern in a region having an uneven structure formed of the apex portion and the like, a photoresist film formed in the region having the uneven structure is exposed to light in the step of forming a frame (a frame pattern) for forming the plated film pattern. Consequently, light is reflected obliquely or transversely from an inclined surface portion of the underlayer. Since the reflected light increases or reduces an exposed region in the photoresist film, the reflected light deteriorates the accuracy in forming the frame pattern. This makes it difficult to form with high accuracy the top pole, particularly the uniform-width portion having a local miniature width. The greater the height of the apex portion on the underlayer, the more noticeable the tendency to deteriorate the accuracy in forming the top pole.